public class HashBuck {
    static class Node {
        public int key ;
        public int val;
        public Node next;
        public Node (int key,int val) {
            this.key = key;
            this.val = val;
        }
    }
    public Node[] array;
    public int usedSize;

    public static final double LOAD_FACTOR = 0.75;

    public HashBuck() {
        array = new Node[10];
    }
    public void put (int key,int val) {
         int index = key  % array.length;
         Node cur = array[index];
         while (cur != null) {
             if (cur.key == key) {
                 cur.val = val;
                 return ;
             }
             cur = cur.next;
         }
         //使用头插法进行插入
        Node  node = new Node(key,val);
        node.next = array[index];
        array[index] = node;
        usedSize++;
        if (calculateLoadFactor() >= LOAD_FACTOR) {
            //扩容
            resize();
        }

    }

    private void resize() {
          Node[] newArray = new Node[2*array.length];
        for (int i = 0; i < array.length; i++) {
            Node cur = array[i];
            while (cur != null) {
                Node curNext = cur.next;
                int index = cur.key % (2 * array.length);
                cur.next = newArray[index];
                newArray[index] = cur;
                cur  = curNext;
            }
        }
        array = newArray;
    }

    private  double calculateLoadFactor() {
        return usedSize*1.0 % array.length;
      }

      public int get(int key) {
           int index = key % array.length;
           Node cur = array[index];
           while (cur != null) {
               if (cur.key == key) {
                   return cur.val;
               }
               cur = cur.next;
           }
           return -1;
      }
}
